Anti-gas lock electric submersible pump

ABSTRACT

An electric submersible pump including a housing having a longitudinal axis extending therethrough; and a plurality of stages disposed within the housing each stage having an impeller and a diffuser, the plurality of stages stackable one upon the other along the longitudinal axis of the housing, wherein one or more of the plurality of stages is a standard flow stage, wherein one or more of the plurality of stages is an anti-gas lock flow stage, and wherein the anti-gas lock flow stages are modified relative the standard flow stages to have decreased incidence of trapped gas.

FIELD

The present disclosure relates generally to electric submersible pumps.In particular, the present disclosure relates to electric submersiblepumps for use in wellbores related to oil and gas production.

BACKGROUND

During various phases of oil and gas operations it may become necessaryto increase pressure and/or withdraw fluid from within a wellbore. Thiscan often be referred to as artificial “lift” or “pressure.” Forexample, after drilling a wellbore and during the withdrawal ofhydrocarbons, it can be necessary to use a pump to increase the pressurewithin a wellbore when natural pressure is insufficient to withdraw thedesired amount of hydrocarbons. An electric submersible pump (ESP) canbe used to provide artificial lift for withdrawing hydrocarbons.

In order to increase pressure in a wellbore, the ESP is often provideddownhole along a portion of a tubing string. The pump can have multiplestages provided within a housing, one stage stacked upon another stage.Gas can be present in the wellbore fluid and can exit the wellboreeither through the pump and production tubing, or up through theannulus. As gas enters an ESP, the pump performance declines forexample, by degrading efficiency. As the amount of gas within the pumpincreases gas lock can occur, preventing flow throughout the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a diagram illustrating an exemplary environment for anelectric submersible pump (ESP) within an electric submersible pumpstring;

FIG. 2 is a diagrammatic cross section view illustrating an exemplaryESP within a housing;

FIG. 3 is a diagram illustrating an exemplary two stage diffuser stackof an ESP;

FIG. 4 is a diagram illustrating an exemplary standard impeller for usein an ESP;

FIG. 5 is a diagram illustrating the difference in curvature between astandard and a first modified impeller;

FIG. 6 is a diagram illustrating a second exemplary modified impellerfor use in an ESP;

FIG. 7 is a diagram illustrating a third exemplary modified impeller foruse in an ESP;

FIG. 8 is a diagram illustrating a fourth exemplary modified impellerfor use in an ESP;

FIG. 9 is a diagram illustrating an exemplary two stage diffuser stackof an ESP;

FIG. 10 is a diagram illustrating a first exemplary ESP according to thedisclosure herein;

FIG. 11 is a diagram illustrating a second exemplary ESP according tothe disclosure herein; and

FIG. 12 is a diagram illustrating a third exemplary ESP according to thedisclosure herein.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts havebeen exaggerated to better illustrate details and features of thepresent disclosure.

In the following description, reference to up or down is made forpurposes of description with “up,” “upper,” “upward,” or “uphole”meaning toward the surface of the wellbore and with “down,” “lower,”“downward,” or “downhole” meaning toward the terminal end of the well,regardless of the wellbore orientation. Correspondingly, the transverse,axial, lateral, longitudinal, radial, etc., orientations shall meanorientations relative to the orientation of the wellbore or tool.Additionally, the illustrated embodiments are illustrated such that theorientation is such that the top of the page is toward the surface, andthe lower side of the page is downhole. A “pump” as used herein caninclude Electric Submersible Pump (ESP). The term pump and ESP are usedinterchangeably within this disclosure.

Several definitions that apply throughout this disclosure will now bepresented. The term “coupled” is defined as connected, whether directlyor indirectly through intervening components, and is not necessarilylimited to physical connections. The terms “inside” or “inner” indicatethat at least a portion of a region is partially contained within aboundary formed by the object. The terms “comprising,” “including” and“having” are used interchangeably in this disclosure. The terms“comprising,” “including” and “having” mean to include, but notnecessarily be limited to the things so described.

Disclosed herein is an electric submersible pump (ESP) having a varietyof different stages and impellers to reduce gas lock within the pump.The ESP can be attached to a downhole tubing string and used forcreating artificial pressure or lift in a wellbore. The pump can have ahousing containing one or more standard flow stages and one or moreanti-gas lock flow stages. The housing can have a head plate and a baseportion at opposing ends, the head plate being at the end nearest thewellhead and the base portion at the end furthest from the wellhead.Each stage can include a diffuser and an impeller to aid in moving ordisplacing fluid and gas. The one or more stages can be stackable oneupon the other, such that one diffuser sits substantially on top ofanother. The stack can be referred to as a diffuser stack. The impellercan be substantially received within the diffuser. The impeller canrotate around a longitudinal axis within the diffuser. During operation,the diffuser remains stationary relative to the housing. To disrupt gasbubble formation, a plurality of anti-gas lock flow stages can be placednear the base portion of the housing, or strategically spaced throughoutthe length of the housing.

The ESP 114 can be employed in an exemplary wellbore pumping system 1shown for example in FIG. 1. The system 1 includes a wellbore 100 havinga wellhead 102 at the surface 104. The wellbore 100 extends andpenetrates various earth strata including hydrocarbon containingformations. A casing 115 can be cemented along a length of the wellbore100. A power source 106 can have an electrical cable 108, or multipleelectrical cables, extending into the wellbore 100 and coupled with amotor 112. It should be noted that while FIG. 1 generally depicts aland-based operation, those skilled in the art will readily recognizethat the principles described herein are equally applicable to subseaoperations that employ floating or sea-based platforms and rigs, withoutdeparting from the scope of the disclosure. Also, even though FIG. 1depicts a vertical wellbore, the present disclosure is equallywell-suited for use in wellbores having other orientations, includinghorizontal wellbores, slanted wellbores, multilateral wellbores or thelike.

Disposed within the wellbore 100 can be a tubing string 110 having anESP 114 forming an electric submersible pump string. The ESP 114 may bedriven by a motor 112. The tubing string 110 can also include a pumpintake 119 for withdrawing fluid from the wellbore 100. The pump intake119, or pump admission, can separate the fluid and gas from thewithdrawn hydrocarbons and direct the fluid into the ESP 114. Aprotector 117 can be provided between the motor 112 and the pump intake119 to prevent entrance of fluids into the motor 112 from the wellbore.The tubing string 110 can be a series of tubing sections, coiled tubing,or other conveyance for providing a passageway for fluids. The motor 112can be electrically coupled with the power source 106 by the electricalcable 108. The motor 112 can be disposed below the ESP 114 within thewellbore 100. The ESP 114 can provide artificial pressure, or lift,within the wellbore 100 to increase the withdrawal of hydrocarbons,and/or other wellbore fluids. The ESP 114 can provide energy to thefluid flow from the well thereby increasing the flow rate within thewellbore 100 toward the wellhead 102

Illustrated in FIG. 2 is one example of an ESP 114. The ESP 114 can havea housing 116 having a head plate 118 and a base portion 120. The headplate 118 can be disposed at the upper portion of the housing 116 andthe base portion 120 can be disposed at the lower portion of the housing116. The housing 116 can further include at least one inlet 160 and atleast one outlet 162. Each inlet 160 has an opening to allow fluids,such as hydrocarbons, to enter the ESP 114 and each outlet 162 also hasan opening to allow fluids to exit after passing through the ESP 114.The housing 116 can receive a diffuser stack 122. Multiple diffuserstacks 122 can be provided in the housing 116. The diffuser stack 122includes one or more stages 124.

Multiple stages 124 can be stacked one upon the other to increase theenergy added to the flow within the wellbore 100. Any number of stagescan be employed, depending on the requirements of the system 1. Longerwellbore holes may require a larger number of stages 124, and thereforelonger diffuser stacks, due to the increased lift requirements as aresult of the increased volume of the wellbore. For example, a 5,000foot long hole may require as many as 50 stages 124 to providesufficient lift. Longer diffuser stacks or ESP's can be provided, forexample, a 10,000 foot long wellbore hole may require as many as 75stages 124. Any number of stages can be employed, however, typicallythere can be anywhere from 10 to 100 stages, alternatively 25 to 75stages.

Each stage 124 of the diffuser stack 122 can be made up of an individualdiffuser 126 and an individual impeller 128 received within the diffuser126. Typically each stage 124 in the diffuser stack 122 is substantiallyidentical, having substantially identical diffusers 126 and impellers128 at each stage. However, as described above, this can lead to gaslock within the pump. Thus, as described in further detail below,several modified stages 124′ (as shown in FIGS. 9-12) can be includedthroughout the pump. The diffuser stack 122 having the one or morestages 124 can be configured to handle various fluids. For example,different types of impellers 128 and diffusers 126 can be employeddepending on the fluids to be pumped, desired pressure or otherrequirements in the system. For example, the fluids to be pumped can beclear liquids, brine, saltwater, hydrocarbons, mud, abrasives or gas, orother wellbore fluids. Accordingly, the impellers and diffusers can beconfigured to accommodate the particular fluids and conditions of thewellbore. The arrangement of the diffuser stack 122 can depend on thewellbore 100 and the hydrocarbon mixture being withdrawn therefrom.

As illustrated in FIG. 2, the impeller 128 is provided to rotate withinthe diffuser 126 about an impeller hub 130. The impeller hub 130 canextend at least partially above the main body of the impeller 128 to bereceived by an adjacent impeller 128 in the stage above. The diffuser126 can also have an aperture through which the impeller hub 130extends. The impeller hub 130 can extend partially above and/orpartially below the main body of the impeller 128 and couple withimpeller hubs 130 above and/or below in a stacking fashion. For example,the portion of the impeller hub 130 extending partially above theimpeller 128 couples with the impeller hub 130 of the stage 124 stackeddirectly above, whereas the portion of the impeller hub 130 extendingpartially below the impeller 128 couples with the impeller hub 130 ofthe stage 124 stacked directly below. The impeller hub 130 of the stage124 at the top of the diffuser stack 122 can be received by the headplate 118. The impeller hub 130 of the stage 124 at the bottom of thediffuser stack 122 can be received at the base portion 120 and coupledwith the motor 112 (shown in FIG. 1). Accordingly, the impeller hubs 130together can form a shaft extending throughout the diffuser stack 122.

The diffuser stack 122 can be compressed within the housing 116 toprevent recirculation of fluid between the one or more stages 124. Thediffuser stack 122 can be compressed between the head plate 118 and thebase portion 120. A compression bearing 132 can be disposed above thehead plate 118 and can apply mechanical compression force on thediffuser stack 122. The base portion 120 can have substantial strengthto resist the compressive force therefore causing the diffuser stack 122to compress. For example, the compression bearing 132 can be a spiderwheel bearing configured to engage threads on the upper portion of theimpeller hub 130 and compress the head plate 118 into the diffuser 126of the uppermost stage 124 in the diffuser stack 122. The compressionbearing 132 can compress the diffuser stack 122 a predetermineddistance, such as from 1/2,500^(th) of an inch to 1/500^(th) of an inch,or alternatively from 1/2,000^(th) of an inch to 1/1,000^(th) of aninch.

Illustrated in FIG. 3 is an example of a two-stage 124 diffuser stack122. One diffuser 126 of one stage 124 can be stacked on top of anotherdiffuser 126 of the adjacent stage 124′. The diffuser 126 can have aside wall 134 forming a contained receiving space 136. The impeller 128′can be substantially received within the diffuser 126 receiving space.The upper portion of the impeller hub 130 can extend beyond the uppersurface of side wall 134 of the diffuser 126. The upper portion ofimpeller hub 130 can have at least one groove 139 formed on the innersurface. The at least one groove 139 can couple with the impeller hub130 with the stage 124 directly above in the diffuser stack 122. As canbe appreciated in FIG. 3, the diffusers 126 can be stacked and the sidewall 134 of each diffuser 126 can form a substantially flush couplingwith the adjacent stage 124.

Illustrated in FIG. 4 is an example embodiment of a standard impeller128 for use in a standard flow stage. The impeller 128 can be receivedin the diffuser receiving space. During operation, the impeller 128 canfloat within the diffuser such that the impeller 128 does not contactthe diffuser side wall 134 (shown in FIG. 3). The impeller 128 can havea top shroud 150, a bottom shroud 152, and a plurality of vanes 148 toimpart energy in the fluid as the impeller 128 rotates within thediffuser 126. The top shroud 150 and the bottom shroud 152 can havediameters that are equal to one another. The plurality of vanes 148 canbe angled to impart energy in a direction corresponding to the pluralityof inlets within the diffuser 126. The angle can be, for example, fromabout 15 degrees to about 40 degrees; in the alternative the angle canbe from about 20 degrees to about 30 degrees. The standard flow stages,or radial flow stages, are designed to target flow ranges below 1000barrels per day (bbl/d). Such stages can generate more head per linearfoot of pump than other stages; however they are sensitive to gasingestion due to the tight radial flow path. As a result, gas can becometrapped within the stage's vanes and block fluid movement throughout thelength of the pump, for example, gas lock. In the illustratedembodiment, the impeller hub 130 extends beyond the upper surface of theimpeller 128. The impeller hub 130 can extend to various lengths, forexample, beyond the lower surface of the impeller 128. The impeller hub130 can be made to extend a larger amount above or below, or an equalamount above and below the main body of the impeller 128. The impellerhub 130 at each impeller can matingly engage with impeller hubs ofadjacent impellers to form a shaft within the ESP.

To prevent gas lock throughout the ESP, modified stages, or anti-gaslock flow stages 124′ (as shown in FIGS. 9-12), can be used to disruptgas bubble formation. The anti-gas lock flow stages 124′ can includemodified impellers 128′, as shown in FIGS. 5-8. In order to disrupt thegas bubble formation, the modified impeller 128′ includes a fluidleakage that is not present in the standard impeller design whichdecreases the incidence of trapped gas. For example, FIG. 5 illustratesa first modified impeller 128′, having a portion of the top shroudremoved. The modified impeller 128′ comprises a plurality of vanes 156,each of the vanes having a curvature less than the curvature of vanes148 present in a standard impeller 128 (as shown in FIG. 4). The flattercurve of the vanes 156 in the modified impeller 128′ aids in thedisruption of gas-bubble formation by increasing the force on the fluidat the trailing edge of the vane per rotation. While FIG. 5 generallydepicts a modified impeller having a portion of the top shroud removed,the impeller could also be modified by having a portion of the bottomshroud removed.

In the alternative, a modified impeller 128′ can be created by providingan exit path for any gas trapped within the anti-gas lock flow stage124′. For example, FIG. 6 illustrates a second type of modified impeller128′ wherein the top shroud 150 has a diameter less than the diameter ofthe bottom shroud 152. By opening the area immediately above the tip ofthe vanes, a fluid leakage point is provided, allowing for trapped gasto escape, and increasing fluid flow and turbulence within the stage. Athird type of modified impeller 128′ is shown in FIG. 7. The modifiedimpeller 128′ can include a plurality of apertures 160, providing thefluid leakage point. The apertures 160 can be present in one of the topshroud 150, the bottom shroud 152, the vanes 148, or any combinationthereof. While the apertures 160 provide the fluid leakage pointnecessary to reduce gas build-up, they can also be a source ofinefficiency throughout the pump by reducing the energy stored in thefluid as it rises through the impeller.

In an alternative embodiment, the modified impeller 128′ as disclosedherein can have a combination of different fluid leakage points. Forexample, FIG. 8 illustrates a fourth modified impeller 128′ having a topshroud 150 with a smaller diameter than the bottom shroud 152 as well asplurality of apertures 160.

An ESP having only anti-gas lock flow stages 124′ would be significantlyless efficient than ESPs having only standard flow stages 124 due to thesignificant decrease in energy stored in the fluid. However, bycombining both anti-gas lock flow stages 124′ and standard flow stages124, a more efficient pump can be produced. As the gas and liquid moveupward through the pump, the gas is compressed back into the fluid. Itis proposed herein, without being bound to any particular theory, thatmost of the compression occurs in the initial stages of the pump. Thus,by placing one or more anti-gas lock flow stages nearest the base plateof the housing, the formation of gas bubbles can be disrupted, therebysignificantly reducing gas buildup throughout the pump. It is believed,as long as the initial stage(s) of the ESP are able to continuouslyoperate and move fluid, the stages above will also maintain continuousmotion; thus preventing gas lock throughout the pump as a whole. Forexample, FIG. 9 is a diagrammatic illustration of a standard flow stage124 on top of an anti-gas lock flow stage 124′ for use in an ESP 114.The stages 124, 124′ can impart energy into fluid flowing through theESP 114. The modified impeller 128′ can induce a pressure differentialwithin the diffuser 126 causing fluid to move from the bottom of thediffuser 126 to the receiving space and then into the standard flowstage 124 above. As can be appreciated in FIG. 9, as the modifiedimpeller 128′ rotates within the diffuser 126 fluid (or hydrocarbons)moves from the anti-gas lock flow stage 124′ to the standard flow stage124 above, adding energy to the fluid flow. While the illustratedembodiment has two stages, it would be obvious to those in the art thatany number of standard flow stages 124 and anti-gas lock flow stages124′ can be employed, depending on the environment and desired flow.

The ESP 114 may include a plurality of anti-gas lock flow stages 124′disposed near the base plate of the housing, as shown in FIG. 10. Forexample, the first 5 stages, alternatively, the first 10 stages,alternatively, the first 15 stages, alternatively the first 20 stages,or alternatively, the first 5-20 stages, within the ESP can be anti-gaslock flow stages 124′. While the initial stages may be anti-gas lockflow stages 124′, the stages disposed on top of the initial set ofanti-gas lock flow stages 124′ may be standard flow stages 124.Alternatively, a majority of the initial 5 stages, or initial 10 stages,or initial 15 stages, or initial 20 stages may be anti-gas lock flowstages 124′ and the remainder standard flow stages 124. Alternatively,the first 5%, or 10%, or 15%, or 20%, or 25% stages, out of the totalnumber of stages in the electric submersible pump, or a majority of suchstages, disposed near the base plate of the housing may be anti-lockstages 124′ and the remainder standard flow stages 124.

The stages may be mixed throughout, having a plurality of anti-gas lockflow stages 124′ mixed amongst a plurality of standard flow stages 124.For example, at least 5% of the stages, or at least 10% of the stages,or at least 15% of the stages, or at least 20% of the stages, or atleast 25% of the stages, out of the total number of stages may beanti-gas lock flow stages 124′ and the remainder standard standard flowstages 124. The anti-gas lock flow stages 124′ may be dispersed atvarious points throughout the ESP, as shown in FIG. 11. For example, theinitial set of stages can be anti-gas lock flow stages 124′ andadditional anti-gas lock flow stages 124′ can be dispersed throughout aplurality of standard flow stages 124 at predetermined locationsthroughout the ESP. Different arrangements can be created, depending onthe intended use for the pump, as well as the targeted flow range.Additionally, the modified impellers 128′ used in the anti-gas lock flowstages 124′ do not have to be the same throughout the ESP, differentmodified impellers 128′ can be used at different points throughout thepump in order to optimize production. For example, fluid mixtures withhigh gas-to-liquid ratios and a low water concentration (<10%) can beproduced better using an anti-gas lock flow stage 124′ designed formarginally grater total volumetric flow.

Alternatively, the ESP can include two or more housings 114 strungtogether, as shown in FIG. 12. For example, the downhole housing 114 caninclude a plurality of anti-gas lock flow stages 124′ and the upholehousing 114 can include a plurality of standard flow stages 124. Thus,any gas that enters the pump is compressed back into the liquid prior toreaching the standard flow stages 124 and preventing gas lock throughoutthe pump. The uphole housings may also include one or more anti-gas lockflow stages 124′ at strategic positions in order to maintain the desiredflow rate. Although FIG. 12 only illustrates two housing, it would beapparent to those of skill in the art that any number of housings couldbe used.

While the above embodiments have been described in detail in theforegoing description, the same is to be considered as illustrative andnot restrictive in character, it being understood that only someembodiments have been shown and described and that all changes andmodifications that come within the spirit of the embodiments are desiredto be protected. Specifically, it should be known that ESP pumps aretypically assembled on site, allowing for the arrangement to becontinuously changed and updated based on the specific needs of theuser. Thus, it would be apparent to one of skill in the art that anyarrangement of standard flow stages 124 and anti-gas lock flow stages124′ could be used.

Furthermore, the above described system can be used in combination witha variable speed drive (VSD) in order to further enhance the systemperformance. For example, as gas is ingested into a pump downhole, thetorque load on the pump is reduced; the loss in load will typicallycause an increase in drive speed throughout the pump. This increase inspeed generates more flow throughout the pump, which will increase thetorque on the driving motor and consuming more current. When a pumpencounters an overwhelming amount of gas within the system the load losscan be extreme resulting in a total system shutdown. However, a VSD canrun a series of gas purging by slowing the speed of the pump in responseto significant load loss, allowing the fluid column in the tubing toreduce velocity and expelling the trapped gas out of the pump'sdischarge. The VSD can also cause an intentional disruption in the fluidflow throughout the pump massaging the trapped gas out of the pump.However, use of a VSD alone is not always effective, use in combinationwith the anti-gas lock flow stages described above increase efficiencyof the VSD by providing stages that are able to support the intentionaldisruption.

Numerous examples are provided herein to enhance understanding of thepresent disclosure. A specific set of statements are provided asfollows.

Statement 1: An electric submersible pump comprising a housing having alongitudinal axis extending therethrough; and a plurality of stagesdisposed within the housing each stage having an impeller and adiffuser, the plurality of stages stackable one upon the other along thelongitudinal axis of the housing, wherein one or more of the pluralityof stages is a standard flow stage, wherein one or more of the pluralityof stages is an anti-gas lock flow stage, and wherein the anti-gas lockflow stages are modified relative the standard flow stages to havedecreased incidence of trapped gas.

Statement 2: An electric submersible pump in accordance with Statement1, wherein the anti-gas lock flow stages have a fluid leakage pointabsent in the standard flow stages thereby decreasing the incidence oftrapped gas.

Statement 3: An electric submersible pump in accordance with Statement 1or Statement 2, wherein the impeller of the one or more anti-gas lockflow stages comprises a top shroud, a bottom shroud, and one or morevanes.

Statement 4: An electric submersible pump in accordance with Statements1-3, wherein the fluid leakage point comprises apertures formed in oneor more of the top shroud, the bottom shroud, and the one or more vanes.

Statement 5: An electric submersible pump in accordance with Statements1-4, wherein the diameter of the top shroud is less than the diameter ofthe bottom shroud, thereby forming the fluid leakage point.

Statement 6: An electric submersible pump in accordance with Statements1-5, wherein the diameter of the bottom shroud is less than the diameterof the top shroud, thereby forming the fluid leakage point.

Statement 7: An electric submersible pump in accordance with Statements1-6, wherein the housing further comprises a head plate and a baseportion.

Statement 8: An electric submersible pump in accordance with Statements1-7wherein an initial set of the plurality of stages nearest the baseportion are anti-gas lock flow stages.

Statement 9: An electric submersible pump in accordance with Statements1-8, wherein the initial set comprises at least 5 stages.

Statement 10: An electric submersible pump in accordance with Statements1-9, wherein the initial set comprises at least 10 stages.

Statement 11: An electric submersible pump in accordance with Statements1-10, wherein a plurality of standard flow stages are stacked on top ofthe initial set of anti-gas lock flow stages, relative the base portion.

Statement 12: An electric submersible pump in accordance with Statements1-11, wherein a majority of an initial set of the plurality of stagesnearest the base portion are anti-gas lock flow stages.

Statement 13: An electric submersible pump in accordance with Statements1-12, further comprising a plurality of standard flow stages and aplurality of anti-gas lock flow stages.

Statement 14: An electric submersible pump in accordance with Statements1-13, wherein the plurality of anti-gas lock flow stages are dispersedthroughout the plurality of standard flow stages.

Statement 15: An electric submersible pump in accordance with Statements1-14, wherein the impeller of the one or more standard flow stagescomprises a top shroud, a bottom shroud, and one or more vanes.

Statement 16: An electric submersible pump in accordance with Statements1-15, wherein the curvature of the one or more vanes of the anti-gaslock flow stage is less than the curvature of the one or more vanes ofthe standard flow stage.

Statement 17: A system comprising a tubing string; and an electricsubmersible pump string coupled with the tubing string, wherein theelectric submersible pump string comprises at least one housing having alongitudinal axis extending therethrough, and a plurality of stagesdisposed within the housing each stage having an impeller and adiffuser, the plurality of stages stackable one upon the other along thelongitudinal axis of the housing, wherein one or more of the pluralityof stages is a standard flow stage, wherein one or more of the pluralityof stages is an anti-gas lock flow stage, and wherein the anti-gas lockflow stages are modified relative the standard flow stages to havedecreased incidence of trapped gas.

Statement 18: A system in accordance with Statement 17, wherein theanti-gas lock flow stages have a fluid leakage point absent in thestandard flow stages thereby decreasing the incidence of trapped gas.

Statement 19: A system in accordance with Statement 17 or Statement 18,wherein the impeller of the one or more anti-gas lock flow stagescomprises a top shroud, a bottom shroud, and one or more vanes.

Statement 20: A system in accordance with Statements 17-19, wherein thefluid leakage point comprises apertures formed in one or more of the topshroud, the bottom shroud, and the one or more vanes.

Statement 21: A system in accordance with Statements 17-20, wherein thediameter of the top shroud is less than the diameter of the bottomshroud, thereby forming the fluid leakage point.

Statement 22: A system in accordance with Statements 17-21, wherein thediameter of the bottom shroud is less than the diameter of the topshroud, thereby forming the fluid leakage point.

Statement 23: A system in accordance with Statements 17-22, wherein theat least one housing further comprises a head plate and a base portion.

Statement 24: A system in accordance with Statements 17-23, wherein aninitial set of the plurality of stages nearest the base portion areanti-gas lock flow stages.

Statement 25: A system in accordance with Statements 17-24, wherein theinitial set comprises at least 5 stages.

Statement 26: A system in accordance with Statements 17-25, wherein theinitial set comprises at least 10 stages.

Statement 27: A system in accordance with Statements 17-26, wherein aplurality of standard flow stages are stacked on top of the initial setof anti-gas lock flow stages, relative the base portion.

Statement 28: A system in accordance with Statements 17-27, wherein amajority of an initial set of the plurality of stages nearest the baseportion are anti-gas lock flow stages.

Statement 29: A system in accordance with Statements 17-28, furthercomprising a plurality of standard flow stages and a plurality ofanti-gas lock flow stages.

Statement 30: A system in accordance with Statements 17-29, wherein theplurality of anti-gas lock flow stages are dispersed throughout theplurality of standard flow stages.

Statement 31: A system in accordance with Statements 17-30, wherein theelectric submersible pump comprises a first housing and a secondhousing, wherein the second housing is disposed uphole of the firsthousing.

Statement 32: A system in accordance with Statements 17-31, wherein thefirst housing comprises a plurality of anti-gas lock flow stages, andthe second housing comprises a plurality of standard flow stages.

Statement 33: A system in accordance with Statements 17-32, wherein theimpeller of the one or more standard flow stages comprises a top shroud,a bottom shroud, and one or more vanes.

Statement 34: A system in accordance with Statements 17-33, wherein thecurvature of the one or more vanes of the anti-gas lock flow stage isless than the curvature of the one or more vanes of the standard flowstage.

Statement 35: A method for preventing gas lock comprising providing anelectronic submersible pump comprising a housing having a longitudinalaxis extending therethrough, and a plurality of stages disposed withinthe housing each stage having an impeller and a diffuser, the pluralityof stages stackable one upon the other along the longitudinal axis ofthe housing, wherein one or more of the plurality of stages is astandard flow stage, wherein one or more of the plurality of stages isan anti-gas lock flow stage, and wherein the anti-gas lock flow stagesare modified relative the standard flow stages to have decreasedincidence of trapped gas; disposing the electronic submersible pump intoa wellbore via a tubing string; and generating a fluid flow through thehousing by rotation of the impeller within the one or more standard flowstages and the one or more anti-gas lock flow stages.

Statement 36: A method in accordance with Statement 35, wherein theanti-gas lock flow stages have a fluid leakage point absent in thestandard flow stages thereby decreasing the incidence of trapped gas.

Statement 37: A method in accordance with Statement 35 or Statement 36,wherein the impeller of the one or more anti-gas lock flow stagescomprises a top shroud, a bottom shroud, and one or more vanes.

Statement 38: A method in accordance with Statements 35-37, wherein thefluid leakage point comprises apertures formed in one or more of the topshroud, the bottom shroud, and the one or more vanes.

Statement 39: A method in accordance with Statements 35-38, wherein thediameter of the top shroud is less than the diameter of the bottomshroud, thereby forming the fluid leakage point.

Statement 40: A method in accordance with Statements 35-39, wherein thediameter of the bottom shroud is less than the diameter of the topshroud, thereby forming the fluid leakage point.

Statement 41: A method in accordance with Statements 35-40, wherein thehousing further comprises a head plate and a base portion.

Statement 42: A method in accordance with Statements 35-41, furthercomprising disposing an initial set of anti-gas lock flow stages nearestthe base portion of the housing.

Statement 43: A method in accordance with Statements 35-42, wherein theinitial set comprises at least 5 stages.

Statement 44: A method in accordance with Statements 35-43, wherein theinitial set comprises at least 10 stages.

Statement 45: A method in accordance with Statements 35-44, furthercomprising disposing a plurality of standard flow stages on top of theinitial set of anti-gas lock flow stages, relative the base portion.

Statement 46: A method in accordance with Statements 35-45, wherein amajority of an initial set of the plurality of stages nearest the baseportion are anti-gas lock flow stages.

Statement 47: A method in accordance with Statements 35-46, wherein theelectric submersible pump further comprises a plurality of standard flowstages and a plurality of anti-gas lock flow stages.

Statement 48: A method in accordance with Statements 35-47, furthercomprising dispersing the plurality of anti-gas lock flow stagesthroughout the plurality of standard flow stages.

Statement 49: A method in accordance with Statements 35-48, wherein theimpeller of the one or more standard flow stages comprises a top shroud,a bottom shroud, and one or more vanes.

Statement 50: A method in accordance with Statements 35-49, wherein thecurvature of the one or more vanes of the anti-gas lock flow stage isless than the curvature of the one or more vanes of the standard flowstage.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, especially inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure to the full extent indicated by thebroad general meaning of the terms used in the attached claims. It willtherefore be appreciated that the embodiments described above may bemodified within the scope of the appended claims.

What is claimed:
 1. An electric submersible pump comprising: a housinghaving a longitudinal axis extending therethrough; and a plurality ofstages disposed within the housing each stage having an impeller and adiffuser, the plurality of stages stackable one upon the other along thelongitudinal axis of the housing, wherein one or more of the pluralityof stages is a standard flow stage, wherein one or more of the pluralityof stages is an anti-gas lock flow stage, and wherein the anti-gas lockflow stages are modified relative the standard flow stages to havedecreased incidence of trapped gas.
 2. The electric submersible pump ofclaim 1, wherein the anti-gas lock flow stages have a fluid leakagepoint absent in the standard flow stages thereby decreasing theincidence of trapped gas.
 3. The electric submersible pump of claim 2,wherein the impeller of the one or more anti-gas lock flow stagescomprises a top shroud, a bottom shroud, and one or more vanes.
 4. Theelectric submersible pump of claim 3, wherein the fluid leakage pointcomprises apertures formed in one or more of the top shroud, the bottomshroud, and the one or more vanes.
 5. The electric submersible pump ofclaim 3, wherein the diameter of the top shroud is less than thediameter of the bottom shroud, thereby forming the fluid leakage point.6. The electric submersible pump of claim 1, wherein the housing furthercomprises a head plate and a base portion.
 7. The electric submersiblepump of claim 6, wherein an initial set of the plurality of stagesnearest the base portion are anti-gas lock flow stages.
 8. The electricsubmersible pump of claim 1, further comprising a plurality of standardflow stages and a plurality of anti-gas lock flow stages.
 9. A systemcomprising: a tubing string; and an electric submersible pump stringcoupled with the tubing string, wherein the electric submersible pumpstring comprises: at least one housing having a longitudinal axisextending therethrough, and a plurality of stages disposed within thehousing each stage having an impeller and a diffuser, the plurality ofstages stackable one upon the other along the longitudinal axis of thehousing, wherein one or more of the plurality of stages is a standardflow stage, wherein one or more of the plurality of stages is ananti-gas lock flow stage, and wherein the anti-gas lock flow stages aremodified relative the standard flow stages to have decreased incidenceof trapped gas.
 10. The system of claim 9, wherein the anti-gas lockflow stages have a fluid leakage point absent in the standard flowstages thereby decreasing the incidence of trapped gas.
 11. The systemof claim 10, wherein the impeller of the one or more anti-gas lock flowstages comprises a top shroud, a bottom shroud, and one or more vanes.12. The system of claim 11, wherein the fluid leakage point comprisesapertures formed in one or more of the top shroud, the bottom shroud,and the one or more vanes.
 13. The system of claim 11, wherein thediameter of the top shroud is less than the diameter of the bottomshroud, thereby forming the fluid leakage point.
 14. The system of claim9, wherein the at least one housing further comprises a head plate and abase portion.
 15. The system of claim 14, wherein an initial set of theplurality of stages nearest the base portion are anti-gas lock flowstages.
 16. The system of claim 14, wherein a plurality of standard flowstages are stacked on top of an initial set of anti-gas lock flowstages, relative the base portion.
 17. A method for preventing gas lockcomprising: providing an electronic submersible pump comprising: ahousing having a longitudinal axis extending therethrough, and aplurality of stages disposed within the housing each stage having animpeller and a diffuser, the plurality of stages stackable one upon theother along the longitudinal axis of the housing, wherein one or more ofthe plurality of stages is a standard flow stage, wherein one or more ofthe plurality of stages is an anti-gas lock flow stage, and wherein theanti-gas lock flow stages are modified relative the standard flow stagesto have decreased incidence of trapped gas; disposing the electronicsubmersible pump into a wellbore via a tubing string; and generating afluid flow through the housing by rotation of the impeller within theone or more standard flow stages and the one or more anti-gas lock flowstages.
 18. The method of claim 17, wherein the anti-gas lock flowstages have a fluid leakage point absent in the standard flow stagesthereby decreasing the incidence of trapped gas.
 19. The method of claim18, wherein the housing further comprises a head plate and a baseportion.
 20. The method of claim 18, further comprising disposing aninitial set of anti-gas lock flow stages nearest a the base portion ofthe housing.